Recently, retina implants have been developed that are intended to be used for the treatment of patients whose viewing ability has gone lost entirely or in part due to retinal defects. As a matter of principle, a light-sensitive chip shall be implanted into the subretinal space below the retina. The chip is provided with a plurality of pixel elements receiving an image projected on the retina through the still intact lens of the eye, for converting same into electrical signals and for further converting same into electrical stimuli via a plurality of stimulation electrodes to stimulate the retinal cells adjacent the chip, in order to reconstruct or improve vision of blind or partially blind patients.
U.S. Pat. No. 4,628,933 discloses a retina implant which, however, is not intended to be used for subretinal implantation but for epiretinal implantation instead, i.e. the light-sensitive chip shall not be implanted into the subretinal space but directly onto the surface of the retina. The stimulation electrodes, therefore, are not provided on the side of the chip facing the lens but on its rear side instead.
It has been found out that for subretinal implants as well as for epiretinal implants it is necessary to feed external energy in order to actively amplify the received light signals and for converting same into stimulation signals for the adjacent cells.
For that purpose, U.S. Pat. No. 4,628,933 suggests to transmit energy to the implant via electromagnetic induction. For that purpose, a receiver coil is wound around the periphery of the implant chip. By means of the receiver coil, radiofrequency energy having been transmitted from an external source of energy which, for example, may be located in an eyeglass frame, is received and is transformed into electrical energy for supplying the chip.
Considering that such a coil must be provided with a sufficient number of windings, must have a considerable coil diameter for an effective coupling of radiofrequency energy and, further, appropriate installations must be provided for rectifying and smoothening the induced alternating current, a chip of that kind would hardly be adapted to be implanted into the human eye due to its substantial dimensions.
For that purpose, subretinal implants have been developed recently which have not been supplied via rf coupling of electromagnetic energy but via invisible infrared radiation which was converted into electrical energy by means of an appropriate photovoltaic layer.
A subretinal implant of the type specified before is disclosed e.g. in WO 98/17343.
However, it must be considered to be disadvantageous in that case that for operating the implant, infrared radiation must continuously be irradiated into the eye.
It is, therefore, an object underlying the invention to provide an improved retina implant being supplied with electromagnetic energy via inductive coupling and which may be implanted into the subretinal space simply and without the risks of complications.
Moreover, a method for manufacturing such a retina implant shall be provided.